Cruising to Improve the Detection of Burmese Pythons in Everglades National Park

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It is not uncommon to see researchers cruising around Everglades National Park (ENP) on what has been a routine basis for the past ten months. Every evening, interns pack into a Chevy Volt for their shift assisting the U.S. Geological Survey in conducting Burmese Python (Python molurus bivittatus) nighttime surveillance through observational surveys. This effort to detect non-native snakes, namely pythons, will improve management efforts for the Burmese Python population in the national park and surrounding areas. Identifying the correlates of increased python activity will allow managers to better focus on their removal based on where python observations are most likely.

Kaycee Faunce, a USGS intern, measures a mud snake, a native but uncommon species in Everglades National Park. Photo credit: Molly Conway.

The Burmese Python, native to southern and southeast Asia, is an invasive species in the Florida Everglades where it has disrupted an ecosystem and exerted large ecological impacts and biological challenges for the national park. More than 30 native species are documented as python prey, and several of these prey populations are now in decline. Pythons are skillful at avoiding detection, and because they are very difficult to find, python control efforts are increasingly difficult for land managers. Though there are not yet credible population-size estimates, the areas from where the pythons are reported continues to expand northward in Florida.

Beginning January 1, 2015, a research plan was set in place for a new study initiating nighttime roadside surveillance efforts to cruise the roads, otherwise referred to as road surveys, in Everglades National Park. As USGS Biologist and Invasive Species Science Branch Chief, Dr. Robert Reed, has said, “...the odds of a trained searcher on foot detecting a python that's known to be in an area are on the order of one per hundred days spent searching the area.” It was fairly obvious a new approach to detection was in order, and Biologist Dr. Bryan Falk was ready to lead the intensive sampling scheme.

What makes this study unique is two-fold - the use of the electric hybrid vehicle as the observation vehicle and the dedication of youth interns for the vast majority of the work. Three-hundred and sixty-five days of monitoring efforts by car from one side of the park to the other requires both wheels and manpower.

The environmental impact and reduction of carbon dioxide emissions was important for the team. By using a hybrid electric vehicle, such as a Chevrolet Volt, they are saving fuel, employing alternative energy sources, and reducing emissions. It’s environmentally responsible. The vehicle is outfitted with a GPS unit with data entry and camera capabilities, snake hooks and bags for the 82-mile route.

For the duration of a year, a single vehicle is used for road surveys to search and identify areas of increased python activity. The team takes into account variables to use as testable correlates, which include observation rates of native snake species, habitat type, brightness, and weather variables.

The surveys take place each and every night, when teams of two set out to document the locations of Burmese Pythons and native snake species. The nightshifts begin when the sun no longer illuminates the sky (astronomical twilight) and last for roughly 3-4 hours. They traverse the main park road, starting at the main park entrance and turning around at Flamingo, a route which transects seven habitat types including: coastal marshes, mangroves, cypress domes, coastal prairies, freshwater sloughs, pinelands, and hardwood hammocks. The route also includes roads to Pahoyokee Overlook and Mahogany Hammock to cover hardwood hammocks, a habitat type not well-represented by traveling the main road alone.

USGS intern Molly Conway measures a snake while wearing bug-protective gear, a necessary precaution for working in Everglades National Park during the wet season. Photo credit: Kaycee Faunce.

When a snake is observed, participants record the species name, coordinates, and time. Native snakes are measured and georeferenced, while Burmese Pythons are collected and transferred to the lab for additional sampling and data collection. Road-cruising data are supplemented with GIS habitat layers, hourly brightness data, and weather data including: temperature, dew point, pressure, wind direction, wind speed, humidity, precipitation, and solar radiation. Researchers will analyze the frequency of observations, habitat type, and weather variability to better understand the full range of weather conditions and potential seasonal effects to determine how snake occurrences vary from day to day and where python observations are the most likely.

So far this year, the project has resulted in more than 2000 snake observations, most of which are of native species. Analysis will not begin until data collection is finished, but some interesting patterns have already emerged. For example, the researchers observed several pythons at night during the winter, a time of the year when pythons were believed to be active mostly during the day.

As research on python management continues to intensify over the coming years, this effort will advance the understanding of when and where pythons are most likely to be found, and take researchers one step closer to the ultimate challenge of locating pythons, animals that are extremely difficult to find even when present in relatively high numbers.

Invasive species are considered to be second only to habitat degradation in terms of negative impacts on the Earth’s ecosystems, and our scientists make up a significant proportion of the global expertise in the rapidly-growing problem of invasive reptiles.

The Daniel Beard Center in Everglades National Park provides the base for most of the field work done on the control of invasive reptiles by USGS Fort Collins Science Center staff. The team works in Everglades National Park, Big Cypress National Preserve, Crocodile Lake National Wildlife Refuge, and other parts of the Greater Everglades Ecosystem focusing on, among other species of concern,...